Machine for pointing drills



Feb. 18, 1941; H. c. SCHUMACHER 2, 56

MACHINE FOR POINTING DRILLS Filed Jan. 30, 1939 3 Sheets-Sheet 1 FIG].FIG.2. FIG.3.' FIG.4. 4 r l4 :2 2 l 2o 5 9 I3 22 INVENTOR HARRY\C.SCHUMACHER imim M w HEM ATTORNEYS v Feb. 18, 1941.

FIG.8.

FIGJI.

- FIGLIO.

HQC. SCHUMACHER MACHINE FOR POINfIING DRILLS Filed Jan. 30, 1939 sSheets-She et 2 INVENTOR HARRY C. SCHUMACHER ATTORNEYS Fb. 18, 1941. QSQHUMACHR 2,232,563

MACHINE FOR POINTING DRILLS Filed Jan. 30, 1959 5 Sheets-Sheet 3 mammalE--i E;

K7 K6 K K3 mag INVENTOR. HARRY C. SCHUMACHER ATTORNEYS Patented Feb. 18,1941 UNITED STATES PATENT OFFICE 10 Claims.

The invention relates to machines for grinding twist drills, and moreparticularly to a construction adapted to accurately form the cuttingedges of the drill so as to be exactly centered in the axis of rotation.

In the manufactureof twist drills the body of the-drill isformed withhelical grooves therein separated from each other by a web portion whichunites opposite segmental cylindrical portions. The strength ofthe-drill depends upon thethic'kness of this web portion,but thegreaterthe thickness thefarther the main cutting edge at the end of the drillwill be removed from the axis of rotation. -It is, therefore, necessaryin forming the cutting end of the drill to cut away the rear side of*the Web for the double purpose of forming auxiliary cutting edges andproviding a necessary clearance. The accuracy of operation of the drilldepends upon forming these auxiliary 2O cutting edges so as to extendexactly to the axis of rotation, but such accuracy in construction is Itis the object of my invention to obtain a construction adaptedior theaccurate pointing of 25 twist drills of any size within predetermined.limits and ofany variation in helical angle. To this end, the inventionconsists in the construction as hereinafter set forth.

In the drawings: 30 Figures 1 to 4 inclusive are diagrams illustratingtwist drills inaccurately and accurately pointed;

Figure 5 is a plan View of the completed drill;

Figure 6 is a side elevation of the machine;

Figure '7 is an enlarged view of a portion of Figure 6, showing thegrinder wheel in position for finishing one-half of the drill;

Figure 8 is a plan view partly broken away of a portion of Figure 6;

Figure 9 is a section taken on line 9-9 of Figure 8;

Figure 10 is a section taken on line 10-! of Figure 9;

Figure 11 is a cross section on line Il--II of Figure. 9;

Figure 12 is a section on line lZ-l 2 of Figure 8;

Figure 13 is a section on line |3--l3 of Figure 8;

Figure 14 is a section on line l4--l4 of Figure 8;

Figure 15 is an elevation of the trimming mechanism viewed in the samedirection as Figure 6;

Figure 16 is a side elevation of the trimming mechanism viewed from theleft of Figure 8.

To better illustrate the functioning of my improved machine, I havediagrammatically represented in Figures 1 to 4 the cutting end of twistdrills accurately and inaccurately formed. Figure 1 illustrates the"endof the drill before the cutting away of the web portion. to form theauxiliary cutting edges and clearance. Figure 2 is a similar viewshowing the web partly cut away, but with the auxiliary cutting edgesnot extending completely to the axis of rotation. Figure 3 is a similarview showing the web cut away more on one side than the other, so thatone of the auxiliarycutting edges extends beyond the axis of rotation.Figure 4 is a. similar View showing the web cut away to center bothauxiliary cutting edges exactly in the axis of rotation.

As shownin Figure 1, l is the web portion of the twist drill and 2 and 3the helical grooves on opposite sides thereof. If such a constructionwithout further formation, were used for drilling then assuming thedirection of rotation as indicated by the arrow, there would be acutting edge extending from 4 to 5 on the side of the webadjac'eiit tothe groove 2, and a cutting edge extending from 6 to I on the side ofthe web adjacent to the groove3. As neither of these cutting edgesextends to the axis of rotation, this would leave an undercutareadefined by the circle 8. In Figure 2 the rear portions of the web onopposite sides of the axisare cut away as indicated at 9 and III to formauxiliary cutting edges II and I2, which however, do not extendcompletely to the axis of rotation. This would leave an undercut areaindicated by the smaller circle l3. In Figure 3 theyweb is cut away atI4 to form a cutting-sedge l5 which extends through and beyond the axisof rotation, while on the opposite side the Web is cut away at IE toform a cutting edge ll extending to the edge I5. This also would leavean uncut area defined by the small circle l8. Finally; in Figure 4 theweb is cut away at l9 and illto form cutting edges 2| and 22 terminatingexactly in the axis of rotation. Such a construction will remove all ofthe material from the axis to the periphery'of the drill, and thecutting edges upon opposite sides of the axis will he so exactlybalanced as to avoid tendency to deflect thedrill in any direction.Figure 5 is a plan view of the cutting end of the drill as formed inFigure 4, 23 and 24 being the main cutting edges formed on oppositesides of the web, and 2| and 22 the auxiliary cutting edges. The cutaway portions extend at substantially the helix angle so that while theweb is reduced in thickness its rear face25 is substantially parallel tothe front face 26 of the helix. This gives the maximum .of said memberrelative thereto.

clearance without unnecessarily weakening the strength of the web.

In designing my machine to be universal in the pointing of drills, thevariables to be considered are: first, the peripheral diameter of thedrill; second, the thickness of the web; and third, the helical angle.It is also essential that with all variations in these factors the drillblank should be mounted so that its finished center will be exactlypositioned with respect to the line of relative movement of the grinderwheel, which I accomplish by the following construction.

My improvements may be either embodied in a machine particularlydesigned for the purpose or may be used as attachments to any standardform of tool grinding machine. Such machines include as essentialfactors: first, a rotary grinder wheel and means for trimming the sameto a predetermined cross sectional contour; second, a work support, andthird, means for relatively reciprocating said grinder wheel and worksupport along a predetermined path. Usually the direction ofreciprocation is rectilinear and provision is made for adjusting the.work or the grinder wheel transversely with respect to the path ofmovement.

Figure 6 illustrates a machine particularly designed for pointing drillsin which A is a suitable base provided with an upwardly extending columnB for supporting an electric motor C, and D is a grinder wheel mountedupon the motor shaft. This grinder is shown as a cupped wheel, which isenclosed within a guard housing E, the latter being cut away at thebottom for exposing the operating portion of the wheel.- Supported onthe base A are guide rails F extending parallel to the plane of rotationof the grinder wheel with their opposite ends secured in bracket membersF. G is a carriage slidable upon the guide rails F, and as shown isformed of a hollow member embracing said rails and having bearings G forengaging the same. Upon the carriage G is mounted a transversely movablecarriage H. This also is preferably formed of a hollow member havingparallel guide rails H extending thereacross at right angles to thedirection of the rails F. The rails H engage bearings H mounted upon thecarriage G,-said bearings being arranged within the hollow member H andso spaced as to provide the necessary movement For moving the carriage Hwith respect to the carriage G the latter is provided with an upwardlyextending bracket bearing G having a detachable cap G I is a rotarymember grooved to engage and to be swiveled in the bearing G andinternally threaded to engage a correspondingly threaded rod I. This rodis secured'at its inner end to the member H by means of a screw I whichalso holds it against rotation. I is a second nut member. engaging thethreaded rod I and I is a collar member sleeved upon the rod Iintermediate the members I and 1 This collar is held from rotation whilebeing free to move axially of the rod I, by means of a, spline Iengaging a spline way I in the rod. The arrangement is such that .byrotation of the member. I the rod I and carriage H will be moved uponthe guideways H, while the member I forms an adjustable stop forlimiting the amount of such movement.

Mounted upon the carriage H is a Work holder J. This includes asupporting and clamping bearing for the drill to be operated upon, astop for the pointed end of the drill, and positioning members forholding the drill with its main cutting edges at a predetermined angleto the plane of rotation of the grinder wheel. There is furtherprovision for adjusting the holder to correspond to the particularhelical angle of the drill, while in each position of adjustment theaxial point of the drill will remain in a fixed plane :parallel to theplane of rotation of the grinder wheel, the construction being asfollows.

The base portion J of the work holder J rests upon a horizontal planesurface H on the carriage H and is pivotally connected thereto by apivot post J The latter is threaded at its lower end to engage themember H; has a cylindrical portion engaging a corresponding bearing inthe member J, and a threaded upper portion for engaging a clamping nutJ. A second post J similar to the post J extends through a set;- mentalslot J in the base member J which slot is concentric with the axis ofthe post J A clamping nut J similar to the nut J serves to hold the basemember J in any position of angular adjustment about the axis of thepost J Rising from the base member J is a portion J of the member Jhaving at its upper end a clamping bearing K for the drills. Thisbearing is so located that the axis of the drill which lies in ahorizontal plane will intersect the vertical axis of the post J Thebearing is preferably in the form of a split cylinder and to adapt itfor holding drills of different diameters it is provided with a seriesof exchangeable bushings K, externally fitting the bearing K andinternally the particular drill to be operated upon. The bushings K areslotted on one side as indicated at K for the passing therethrough of aclamping tongue K directly contacting with the drill. The tongue isoperated by a revoluble rod K which has a pivotal engagement K with acentral socket in the tongue, and is threaded to engage a nut K securedin a recess in the member J". At the outer end of the rod is anoperating handle K which when revolved will move the rod axially,carrying with it the tongue K Thus, after the drill is positioned it maybe clamped to securely hold the same. The bushings K are held fromdisplacement by a set screw K.

As has been stated, the point of the drill must be accurately positionedand also the drill must be angularly adjusted about its axis into apredetermined postion. These functions are performed by the followingconstruction.

Secured to one side of the member K in a vertical plane transverse tothe axis of the drill is a casing L which is longitudinally slotted toform guideways for the shanks L and L of cooperating locating members.The jaws of these locating members project beyond the casing L,

and are so fashioned as to bear against the main I cutting edges at theend of the drill on opposite sides of the axis thereof and to properlyposition the same angularly about said axis. The end of the upper jaw Lbears directly against thecutting edge, while the jaw L is in the formof a hook, the inner face of which bears against the other cutting edge.Also, the inner face of the shank L forms a stop for the end of thedrill which is located in the vertical axis of the post J The shanks Land L are partly cut away at L and L to receive coil springs L bearingat their rear ends against the shoulders on said shanks, while theirforward ends bear against a pin L extending vertically through thecasing L. Thus, these springs resiliently urge the shanks L and" Lrearward in mar guideways in the casmg I The rear portion ofthe casing Lis cut" awayto forma recess in which is located an adjustable bl-ock- M.The forward face of this block has-cam-surfaces M and M which inclineoppositely from the center of the block and are adapted torespectivelyengagecorresponding inclined faces'L 'and L at'the rearendsof the shank s L and L The blockM is provided with a'threadeda-perturefor engaging the threaded portion M of a rotary member Mextending vertically through the casing L and swiveled therein.- Asshown,- this member has a head portionlVI bearing on-the top of thecasing and a collar M at its lower endbearing against the lower face ofthe casingythereby holding it from vertical movementwhile permittingfreerotation.

In the central position of the block M the shanks L and L will be heldso that the clamping faces of the jaws L and L will be inalignment withtheir adjacent endsinuthe-vertical axis of the post J When, however, themember M is revolved to move the block M in a downward direction,the-cam'face M will move the shank L 'outward, while the cam face M willbe withdrawnfromtheshank L to permit the latter to moverearwardunder-the actuation of its spring ciently for theengagementof the drill,after whichan'opposite rotation of the member M willmove the-jawsintocontact with the main cuttingedges of the drill. The drill is thusproperlylocated, after which it is clamped by the operation-ofthe handle'K actuating the tongue K thereby rigidlysecuring the drill foroperationthereuponby the grinder wheel.

It-is essential to the proper functioning ofthe machinethat the grinderwheelshould be fashioned toa cross'sectional contour correspondingto'the clearancerecess in the finished tool. This fashioning ofthe-grinder is accomplished by a trimming mechanism which is mounted onthe carriage H'and'whioh is of the following construction. N is a postprojectingvertically upward from one side of the carriage H so as to bespaced from the post J N is a bracket member havingaportion N sleevedentire post Nand a depending'portion N bearing "against'the side of the'carriage H'to preventrotation on the post. The bracketN' is formedwith asegmental portion N having a T-shaped segmental slot N therein. N is ahead member having a segmental rib N' engaging the slot N and N is aclamping bolt passing through the head N providedatits innerend withaT-head N in the slot'Ni, and ,at'its outer endengaginga clamping nut NThe construction is such that the head N may be adjusted around toanydesired position on the segment N and held in this position bytightening the clamping nut N Journaled within the head N is a rockshafthaving on one end a; rock arm 0 and on its opposite end an actuatingcrank handle 0 At the free end of the rock arm 0' is a cylindricalsocket O for the. reception of a dresser or trimmer bar 0 extendingobliquely in relation to the plane of the rock arm. 'An adjustment screw0 will move the dresser bar axially and when properly positioned thecutting surface of the end of this dresser bar should be located at thecenter of theysegment N Operation i To set-the machine ready foroperation in pointingia drill, a bushing K is first selected having aninternal diameter correspondingto theparticular drill to bemounted; Thisbushing is then engaged with the split clampingbe'a-ringK and securedtherein by the set screw K. The drill-is then inserted through thebushing and 5 its end adjusted until it contacts with the inner faceof-the shank L the jaws;L and L being' first separated: sufficientlyforthe reception 1 of the drill. The rotary member M is then revolved inadirection to movethe jaws L and L toward each other until" they engagewith the main cutting edges "of the drill to holdthe latter againstrotation.- The handle K is then turnedto project the'tongue Kthrough-the slot K and to clamp the drill rigidly within the bushing.The work holder J J is then adjusted-about the pivot J to correspond to.the helical angle of the drill, andwhen properly adjusted is clampedin"this position by tightening the clampingnuts J andJ;

Trimming of the grinder It being assumedthat the dresser bar 0 has. beenproperlyposit-ioned in its socket 0 the head N is adjusted around thesegment N to an 5-- angular position corresponding to the angle of thejaws L andL or any suitable angle, and then clamped in this position bythe nut N The carriage G is then moved to position thedresserin thevertical axial plane of the grinder 36 wheel, after which thecrankhandle 0 is oscil lated to move thedresser upward and downward acrossthe outer face of the grinder wheel. At. the same time, the member I isrevolved to adjust the carriage H transversely toward the: 5 grinder asfast as necessary to perform the trimming. When the face P of thegrinder wheel; has been properly trimmed, the nut I is rotativelyadjusted upon the threaded red 1' until;

' it bears against the collar I with the latter bear- 0* ing against therotary adjustment member I. The member I will then constitute a stopwhich definitely locates the position of .the carriage-H;

at the point designated 0r axis of the pivot J Subsequent or priorto thetrimming of theface; 52' P the peripheral face Q of the wheel may be.trimmed by first adjusting the head N aroundthe segment N so that thedresser O is substantially in the plane of rotation of said wheel. Thecrank handle 0 is then oscillated to move the dresser back and forthsufficiently to dress the periphery of the wheel. At the completion ofboth of these operations the apex of the angle in the cross sectionalcontour of the grinding wheel:- will be in exact alignment with thecenter'of the 5 5i positioned drill.

The machine is now in condition for the performance of the grindingoperation, it being only necessary to first adjust the rotary member Ito withdraw the carriage I-Iaway from the grinder 60" wheel sufficientlyto clear the drill. The work holder and grin'der wheel are thenrelatively. reciprocated while at the same time the member I is rotatedto gradually feed the carriage toward the wheel, this effecting theprogressive grinding of the side of the drill above itsaxis. Thisgrinding will be completed when the member I -is stopped from furthermovement by the member I The drill is next released in its clampingbearing K, so as to permit of rotating it through an angle of afterwhich it is again clamped. The grinding operation is then. repeated togrind the clearance in the opposite side of the drill. Thus, at thecompletionof both grinding operations the drill'will be properly ground,the tw'o nl auxiliary cutting faces being exactly centered in the axisofthe drill. What I claim as my invention is: 1. The combination of agrinder wheel formed to a predetermined angular cross sectional contour,a carriage mounted for relative reciprocation, a work holder pivotallymounted on said carriage to be adjustable about an axis perpendicular tothe direction of reciprocation, means for clamping upon said work'holder a tool to be ground with its rotational axis in a plane parallelto the direction of movement of said carriage and intersecting saidperpendicular axis, said plane being tangent to the apex of the angularcross ,sectional contour of said grinder wheel, a stop for locating theend of said tool at the point of intersection of saidaxes, means forlocking said work holder in an adjusted position about saidperpendicular axis corresponding to the particular helical angle, of thetool to be ground, and

means for moving said work holder transversely to the direction ofreciprocation to gradually feed said grinder wheel into the work and tofinally bring said point of intersection into the path 5 of the apex ofthe angular cross sectional contour 0 -tion, a work holder pivotallymounted on said carriage to be adjustable about an axis, perpendicularto the direction of reciprocation, means for clamping upon said Workholder a tool to be ground with its rotational axis in a plane parallelto the direction of movement of said carriage and intersecting saidperpendicular axis, said plane being tangent to the apex of the angularcross sectional contour of said grinder wheel, a stop for locating theend of said tool at the point of intersection of said axes, means forlocking said work holder in an adjusted position about saidperpendicular axis corresponding to the particular helical angle of thetool to be ground, means for moving said work holder transv versely tothe direction of reciprocation to gradually feed the work into the pathof said grinder wheel, and means for limiting said transverse movementto the position where said point of intersection lies in the path of theapex of the cross sectional contour of said grinder wheel.

3. The combination of a grinder wheel formed to a predetermined angularcross sectional contour, a main carriage mounted for relativereciprocation, a transverse carriage mount-ed on ,said main carriage, awork holder pivotally mounted on said transverse carriage to beadjustable about an axis perpendicular to the direction ofreciprocation, means for clamping upon said work holder a tool to beground with its rotational axis lying in a plane parallel to thedirection of movement of said carriage and tangent to the apex of theangular cross sectional contour of the said grinder wheel, saidrotational axis intersecting said perpendicular axis, a stop 65 forlocating the end of the tool at the point of intersection of said axes,means for locking said work holder in an adjusted position about saidperpendicular axis corresponding to the particular helical angle of thetool to be ground, and

70; means for limiting the movement of said transverse carriage atapoint where said point of intersection lies in the path of said apex.

4. The combination with a grinder wheel and a main carriage mounted forrelative reciproca- 75 tion, of a transverse carriage mounted on saidmain carriage, a work holder pivotally mounted on said transversecarriage to be adjustable about an axis perpendicular to the directionof reciprocation, means for clamping upon said work holder a tool to beground with its rotational axis intersecting said perpendicular axis andits end located at the point of intersection, means for locking saidwork holder in an adjusted position about said perpendicular axiscorresponding to the particular helical angle of the tool to be ground,means for trimming said grinder wheel to an angular cross sectionalcontour, such that in the relative reciprocation of said main carriageand grinder wheel said point of intersection will lie in the path of theapex of said angular cross sectional contour, and a stop for limitingthe movement of the transverse carriage with the parts in such relation,whereby said transverse carriage when withdrawn to clear the work fromsaid grinder wheel may be gradually fed toward said stop and limited bythe latter when aid apex reaches the exact rotational center of thetool.

5. The combination with a grinder wheel and a main carriage mounted forrelative reciprocation, of a transverse carriage mounted on said maincarriage, a work holder pivotally mounted on said transverse carriage tobe adjustable about an axi perpendicular to the direction ofreciprocation, means for clamping upon said work holder a tool to beground with its rotational axis intersecting said perpendicular axis andits end located at the point of intersection, means for locking saidwork holder in an adjusted position about said perpendicular axiscorresponding to the particular helical angle of the tool to be ground,trimming mechanism also mounted on said transverse carriage adapted totrim said grinder wheel to an angular cross section such that in thesame position of said transverse carriage during reciprocation of saidmain carriage the apex of said angular section will pass through thepoint of intersection of said tool axis and perpendicular axis, and astop for said transverse carriage in this same position limiting itsmovement toward the grinder Wheel while permitting withdrawal of thecarriage in the opposite direction.

6. In a machine of the character described, a work holder including acylindrical bearing, an exchangeable bushing secured Within and fittingsaid cylindrical bearing having concentric inner and outer surfaces andan internal dimension corresponding to the tool to be ground, saidbushing being longitudinally slotted in one side thereof, and clampingmeans for the tool including a tongue member extending longitudinally ofand. through said slot into direct engagement with the tool whereby thelatter is clamped with its axis coincident with the axis of saidcylindrical bearing.

7. In a machine of the character described, a work holder comprising acylindrical bearing, an exchangeable bushing for said bearing having an.internal diameter corresponding to that of the tool to be ground, saidbushing having a slot extending through one side thereof, a tonguemember extending longitudinally of and through said slot, and a screwcentrally pivotally engaging said tongue member to move the same intoclamping contact with the tool while permitting accurate alignmenttherewith of its clamping face whereby said tool is clamped with itsaxis coincident with the axis of the cylindrical bearing.

8. In a machine of the character described,

pivotally mounted on said carriage to be adjustable about an axisperpendicular to the direction of movement of said carriage, means forlocking said work holder in different positions of angular adjustment,means on said work holder for clamping a tool with its rotational axisintersecting said vertical axis, a pair of members slidably secured onsaid work holder to extend perpendicular to said rotational axis and ina plane of said vertical axis, jaws on said members fashioned to engagethe main cutting edges of the tool and to position the same about saidrotational axis, and means for adjusting said members to move said jawsequally on opposite sides of the point of intersection of said verticaland rotational axes.

9. In a machine of the character described, the combination with acarriage, of a work holder pivotally mounted on said carriage to beadjustable about an axis perpendicular to the direction of movement ofsaid carriage, means-for locking said work holder in different positionsof angular adjustment, means on said work holder for clamping a toolwith its rotational axis perpendicular to and intersecting said verticalaxis, a pair of members slidably mounted on said work holder to extendperpendicular to said rotational axis in the plane of said verticalaxis, jaws on said members fashioned to engage the main cutting edges ofthe tool on opposite sides of the axis thereof and to position the sameabout said rotational axis, one of said members forming a stop for theend of the tool, and means for adjusting said members to move said jawsequally and oppositely upon opposite sides of the point of intersectionof said rotational and vertical axes.

10. In a machine of the character described, a work clamping andpositioning means comprising a supporting head, a cylindrical bearing,an exchangeable bushing secured within said cylindrical bearing andhaving an internal diameter corresponding to the tool to be operatedupon, said bushing having a slot in one side thereof,

a tongue engaging said slot, a screw mounted on said head for adjustingsaid tongue to directly engage the same with the tool to be clamped, apair of members slidably mounted on said head to extend perpendicular tothe rotational axis of the tool, jaws on said members fashioned toengage the cutting edges of the tool on opposite sides of the axisthereof, and means for simultaneously adjusting said members to movesaid jaws equally and oppositely on opposite sides of the axis of saidtool.

HARRY C'. SCHUMACHER.

